Conventional apparatus for filling motor vehicle fuel tanks invariably include a hand-held "pistol type" nozzle incorporating a trigger and some kind of automatic cut-off device which is actuated to stop the flow of liquid when the liquid level in the tank reaches the delivery conduit of the nozzle. Since the conduit is not connected to the inlet port of the tank in any way, but is merely thrust loosely into it, the danger of contamination is considerable. Moreover, such a system--known as "splash-filling"--is generally limited to a flow-rate of perhaps 135 liters per minute. Thus, "splash-fillings" are appropriate only for such applications as roadside gas stations and the like, and are totally unsuited to situations in which heavy construction and mining equipment --for instance Unimogs--must be continually serviced as rapidly as possible.
It has been proposed to provide refuelling apparatus including a receiver mountable in a sidewall of a tank or container, close to the bottom, and a refuelling nozzle adapted to be received in the receiver. Such apparatus is disclosed, for example, in specifications relating to U.S. Pats. No's 3,662,793 and 3,674,061. In these and related apparatus', both the receiver and the nozzle have normally closed valves which open in response to the mating of the two parts. The nozzle is equipped with such a normally--closed "snap-acting" valve which is cocked open during the filling operation but snaps closed in response to rise in back-pressure. During the filling operation a tank vent is open but closes in response to the rise in the liquid level which thus creates the back-pressure.
The previously know apparatus had a veritable plethora of component parts requiring continuing maintenance, the piston rod was spring-biased but performed unsatisfactorily. In later developments the spring was replaced by a flexible and resilient diaphragm but this proved to be even more unsatisfactory inasmuch that foreign matter entrained in the fuel was found to tend to seriously affect diaphragm cut-off with possible subsequent rupture of the diaphragm itself.
In practice it was found that even pressures of no more than 70 p.s.i. could cause rupture of the diaphragm, thus diaphragm replacement is a major maintenance problem. In fact, pressures in excess of 90 p.s.i. are not uncommon.
It was also found that the barrel--as that referenced 137 in FIG. 3 of U.S. Pat. No. 3,674,061--was very prone to crack during heavy engagement operation. Moreover, the stayback-rod is prone to wear and breakage.